Singapore received the first of its two newly rebuilt Västergötland -class (Type A-17) submarines from Sweden on 17 August. The Archer and sister Swordsman were purchased in 2005 and underwent an extensive upgrade and modernization effort, including the addition of an advanced air-independent propulsion system that permits extended, quiet underwater operations. Other modifications to the class include the installation of an enhanced climate-control system so the submarines, initially built in the 1980s for service off the frigid Swedish coast, will be able to operate effectively in the tropical climates of Singaporean waters. As built, the class originally consisted of four submarines, the Västergötland , Hälsingland , Södermanland , and Östergötland . The latter two were modernized for Swedish service, while the Västergötland and Hälsingland were placed in reserve prior to their 2005 purchase by Singapore. Each boat in the class displaces 1,500 tons when submerged and is fitted with nine bow torpedo tubes (six 533-mm and three smaller 400-mm). This provides a maximum weapons loadout of 12 larger 533-mm torpedoes and six smaller 400-mm weapons.